In modern mining, geologic surveys and other techniques estimate the size and shape of mineral and/or ore configurations before their removal in a mining operation. The ore and mineral deposits exist in layers or veins at varying depths below ground. For example, deposits of coal can be divided into multiple layers of substantially horizontal planes of varying thickness and at various depths such that several deposits or veins lie at different levels spanning hundreds of feet below ground. Such layers of mineral and ore deposits are often not completely horizontal but have a pitch or slope. Because of the three dimensional sloping layers, the deposits are generally mined from the shallowest end of the deposit in a down slope direction.
In general the rock and earth disposed on top of a mineral or ore layer is referred to as “overburden”. In open pit mining, the overburden atop a first uppermost layer is removed to substantially expose a strip of the mineral or ore deposit. The exposed deposit is then accessible to be removed by mining the uncovered portion and transporting it from the mine for shipment or other processing. Overburden is then removed from above a next adjacent strip of the first layer deposit to substantially expose more of the first deposit layer for removal by mining and shipment.
In open pit mining, once a portion of the uppermost deposit layer is mined and removed, the rock that had been sandwiched between the uppermost layer and the and the next lower deposit layer is exposed and is the overburden atop the next lower layer. Accordingly, the open pit process mining continues by removing strips of that overburden to generally expose the next deposit layer, in a sequential process that continues until successive deposit layers are exhausted. Depending on the size of the deposit, each strip may be several miles in length and is typically about 100 or more feet in width depending on the type of equipment used for the mining operation and other factors such as the size and pitch of the deposit layer.
As open pit mining continues, overburden removal above each deposit layer forms steps or benches. At each step, multiple removal operations increase efficiency in mining the ore or other minerals within the deposits. Multiple operations, however, take some time, and can be cost prohibitive if projected mining yields are not sufficiently high.
The valuable deposit layers are generally much smaller than the layers of overburden. Thus, the most labor intensive task in open pit mining is the removal of the overburden.
In one conventional mining method, a bucket wheel excavator 500, as illustrated in FIG. 1A, loads overburden 29 onto dump trucks 180. A single bucket wheel excavator 500 may cost on the order of One-Hundred Million Dollars ($100,000,000) and require a trained crew of 6 to 8 persons to operate.
As an alternative to a bucket wheel excavator, shovels, drag lines or other bucket type equipment are often used to remove overburden. For example, FIG. 1B illustrates a conventional operation where a shovel 502 loads large oversized dump trucks 180 which deposit their materials into a hopper on a centrally located apron feeder 550. The apron feeder 550 may feed a sizer that reduces oversized chunks of overburden to a size manageable by a conveyor 506 or other means of transport that carries the removed overburden away from the active mining area.
In a conventional mining operation, the apron feeders 550 is typically located at a semi-permanent position where overburden is trucked and deposited to a feed end of the apron feeder. When initially positioned or relocated, an apron feeder 550 is traditionally moved in a direction aligned with the feeder's conveyor operation so that they are essentially backed into a desired location. It is known in the art to provide apron feeders 552 with wheels or crawler undercarriage in line with the feeder operation for the purpose of positioning the apron feeders 552 such as illustrated in FIGS. 2A and 2B.
Applicants have recognized that it would be desirable to provide a method and system of open pit mining that reduces or eliminates the need for reliance on complicated and expensive equipment such as bucket wheel excavators and efficiently uses the necessary equipment. Applicants have in particular recognized that more efficient mining can be conducted through the creative expanded use of apron feeders in the mining operation.
Further, applicants have recognized that improved apron feeder designs may be employed to prevent costly operational stoppages due to the need for cleaning clogged material from an apron feeder.